bpo-41810: Reintroduce `types.EllipsisType`, `.NoneType` & `.NotImplementedType` #22336

BvB93 · 2020-09-21T10:19:20Z

See the relevant BPO for more details: https://bugs.python.org/issue41810.

https://bugs.python.org/issue41810

the-knights-who-say-ni · 2020-09-21T10:19:23Z

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BvB93 · 2020-09-21T10:34:11Z

For reference: I just signed the CLA a few minutes ago.

`type(NotImplemented)` and `type(None)` have, respectively, been replaced with `types.NotImplementedType` and `types.NoneType`

…he docs

ericvsmith

I've not done a thorough review yet. These comments are just about the blurb.

Misc/NEWS.d/next/Library/2020-09-20-15-14-05.bpo-41810.7l8lyV.rst

bedevere-bot · 2020-09-21T20:11:01Z

A Python core developer has requested some changes be made to your pull request before we can consider merging it. If you could please address their requests along with any other requests in other reviews from core developers that would be appreciated.

Once you have made the requested changes, please leave a comment on this pull request containing the phrase I have made the requested changes; please review again. I will then notify any core developers who have left a review that you're ready for them to take another look at this pull request.

BvB93 · 2020-09-21T20:34:01Z

The PR would be easier to review if you hadn’t tried to fix all occurrences of type(......). That could then be done in one or several follow up PRs. Or possibly just skipped until there is demand.

If you want I can remove those changes; they're localized to 0a97a88 and 2791a23 so reverting them should be straightforward.

gvanrossum · 2020-09-21T20:41:15Z

If you want I can remove those changes; they're localized to 0a97a88 and 2791a23 so reverting them should be straightforward.

@ericvsmith, what do you think?

ericvsmith · 2020-09-21T21:29:56Z

I do think it would be easier to review if they were moved to a separate PR, even if it's on the same bpo.

Reverts python@2791a23 and python@0a97a88. Save this for a follow up.

BvB93 · 2020-09-21T21:42:18Z

I do think it would be easier to review if they were moved to a separate PR, even if it's on the same bpo.

The changes have been reverted as of 84ebe18.

gvanrossum

I think the docs for the three special objects should not start with “The sole value of the type ...”.

The first sentence should serve as a brief summary of what the object is used for. You can then follow up with the detail about its singleton type.

Otherwise LGTM. Thanks for your patience!

ericvsmith

This looks good to me!

ericvsmith · 2020-09-21T22:13:14Z

I think the docs for the three special objects should not start with “The sole value of the type ...”.

It's just mirroring the existing documentation for None. But I agree that moving the "the sole value" sentence (or sentence fragment) to the end of the description would be an improvement.

terryjreedy · 2020-09-22T05:28:33Z

I did not particularly want the change in IDLE, because 1) I am not sure I prefer it (partly because of the extra import) and I don't know that PEP-8 'mandates' it*, and 2) I cannot backport it to actively maintained 3.8 and 3.9 code, so it would cause a merge conflict if I patched that section of code. I checked that the latter seems unlikely in this particular case.

I think the effort to 'sanitize' all existing code is futile, since people will continue to put type(None) in code. Consider leading existing code alone.

terryjreedy

Approved, but only with misleading wording fixed.

terryjreedy · 2020-09-22T05:17:18Z

Doc/library/constants.rst

@@ -19,14 +19,15 @@ A small number of constants live in the built-in namespace.  They are:

 .. data:: None

-   The sole value of the type ``NoneType``.  ``None`` is frequently used to
+   The sole value of the type :data:`types.NoneType`. ``None`` is frequently used to


"The sole value of the type NoneType" is most easily read (parsed) as referring to NoneType's usefulness. I expected it to be followed by 'is to ...' and initially read 'is frequently' as a grammatical error. It took awhile to realize that this is a convoluted way to say 'None'. I strongly recommend a rewording.

Suggested change

The sole value of the type :data:`types.NoneType`. ``None`` is frequently used to

''None'' is the only instance of :data:`types.NoneType`. It is frequently used to

types.NoneType is already twice identified as a type, so a third mention is not needed.

Based on your and Guido's feedback (#22336 (review)) I'm proposing something like this:

.. data:: None An object frequently used to represent the absence of a value, as when default arguments are not passed to a function. Assignments to ``None`` are illegal and raise a :exc:`SyntaxError`. Sole instance of the :data:`types.NoneType` type.

Any thoughts?

That's much better, I think. Although I'd make the last sentence (with the correct markup): "None is the sole instance of the NoneType type."

terryjreedy · 2020-09-22T05:21:55Z

Doc/library/constants.rst

+   Sole value of the type :data:`types.NotImplementedType` and a
+   special value which should be returned by the binary special methods


See above. Use a parallel construction.

Suggested change

Sole value of the type :data:`types.NotImplementedType` and a

special value which should be returned by the binary special methods

``NotImplemented is the only instance of :data:`types.NotImplementedType`. It is a

special value which should be returned by the binary special methods

terryjreedy · 2020-09-22T05:22:52Z

Doc/library/constants.rst

@@ -59,7 +60,8 @@ A small number of constants live in the built-in namespace.  They are:
 .. index:: single: ...; ellipsis literal
 .. data:: Ellipsis

-   The same as the ellipsis literal "``...``".  Special value used mostly in conjunction
+   The same as the ellipsis literal "``...``" and sole value of the type


Suggested change

The same as the ellipsis literal "``...``" and sole value of the type

The same as the ellipsis literal "``...``" and the only instance of

terryjreedy · 2020-09-22T05:25:55Z

Doc/whatsnew/3.10.rst

+
+Reintroduced the :data:`types.EllipsisType`, :data:`types.NoneType`
+and :data:`types.NotImplementedType` classes, providing a new set
+of types readily interpretable by type checkers.


I think this and the blurb are fine, providing a reason without saying either that this is the only reason or that these should be use everywhere.

bedevere-bot · 2020-09-22T05:29:52Z

A Python core developer has requested some changes be made to your pull request before we can consider merging it. If you could please address their requests along with any other requests in other reviews from core developers that would be appreciated.

Once you have made the requested changes, please leave a comment on this pull request containing the phrase I have made the requested changes; please review again. I will then notify any core developers who have left a review that you're ready for them to take another look at this pull request.

Addresses python#22336 (comment), python#22336 (comment) & python#22336 (comment)

BvB93 · 2020-09-22T14:29:23Z

@terryjreedy the documentation changes have been implemented as of 23ed559.

* origin/master: (27 commits) bpo-41428: Fix compiler warnings in unionobject.c (pythonGH-22388) bpo-41654: Fix compiler warning in MemoryError_dealloc() (pythonGH-22387) bpo-41833: threading.Thread now uses the target name (pythonGH-22357) bpo-30155: Add macros to get tzinfo from datetime instances (pythonGH-21633) bpo-33822: Update IDLE section of What's New 3.8 (pythonGH-22383) bpo-41844: Add IDLE section to What's New 3.9 (GN-22382) bpo-41841: Prepare IDLE News for 3.10 (pythonGH-22379) bpo-37779 : Add information about the overriding behavior of ConfigParser.read (pythonGH-15177) bpo-40170: Use inline _PyType_HasFeature() function (pythonGH-22375) bpo-40941: Fix stackdepth compiler warnings (pythonGH-22377) bpo-40941: Fix fold_tuple_on_constants() compiler warnings (pythonGH-22378) bpo-40521: Fix PyUnicode_InternInPlace() (pythonGH-22376) bpo-41834: Remove _Py_CheckRecursionLimit variable (pythonGH-22359) bpo-1635741, unicodedata: add ucd_type parameter to UCD_Check() macro (pythonGH-22328) bpo-1635741: Port _lsprof extension to multi-phase init (PEP 489) (pythonGH-22220) bpo-41513: Improve order of adding fractional values. Improve variable names. (pythonGH-22368) bpo-41816: `StrEnum.__str__` is `str.__str__` (pythonGH-22362) bpo-35764: Rewrite the IDLE Calltips doc section (pythonGH-22363) bpo-41810: Reintroduce `types.EllipsisType`, `.NoneType` & `.NotImplementedType` (pythonGH-22336) bpo-41602: raise SIGINT exit code on KeyboardInterrupt from pymain_run_module (python#21956) ...

…mentedType` (pythonGH-22336) closes issue 41810

the-knights-who-say-ni added the CLA not signed label Sep 21, 2020

bedevere-bot added the awaiting review label Sep 21, 2020

BvB93 changed the title ~~BPO-41810: Reintroduce types.EllipsisType~~ bpo-41810: Reintroduce types.EllipsisType Sep 21, 2020

Bas van Beek added 5 commits September 21, 2020 12:28

Reintroduced types.EllipsisType

00639fc

Replaced type(...) and type(ellipsis) with types.EllipsisType

0a97a88

Added EllipsisType to the documentation

8aecfd5

Added Misc/NEWS.d and whatsnew entries

4066b4b

Updated the acknowledgements

307dcc1

BvB93 force-pushed the ellipsis branch from 904bd18 to 307dcc1 Compare September 21, 2020 10:29

csabella removed the CLA not signed label Sep 21, 2020

the-knights-who-say-ni added the CLA not signed label Sep 21, 2020

Bas van Beek added 3 commits September 21, 2020 20:32

Reintroduced types.NoneType and types.NotImplementedType

9fc1381

Replaced type(NotImplemented) and type(None)

2791a23

`type(NotImplemented)` and `type(None)` have, respectively, been replaced with `types.NotImplementedType` and `types.NoneType`

Added types.NoneType & types.NotImplementedType to whatsnew and t…

da1ab85

…he docs

BvB93 requested review from berkerpeksag, ericvsmith, gvanrossum, ilevkivskyi, rhettinger, terryjreedy and tiran as code owners September 21, 2020 18:34

the-knights-who-say-ni added CLA signed and removed CLA not signed labels Sep 21, 2020

BvB93 changed the title ~~bpo-41810: Reintroduce types.EllipsisType~~ bpo-41810: Reintroduce types.EllipsisType, .NoneType & .NotImplementedType Sep 21, 2020

ericvsmith requested changes Sep 21, 2020

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bedevere-bot added awaiting changes and removed awaiting review labels Sep 21, 2020

Explicitly mention static type checkers

33caa6f

Revert the type(...) to types.... replacements

84ebe18

Reverts python@2791a23 and python@0a97a88. Save this for a follow up.

gvanrossum reviewed Sep 21, 2020

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ericvsmith approved these changes Sep 21, 2020

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bedevere-bot added awaiting merge and removed awaiting changes labels Sep 21, 2020

terryjreedy requested changes Sep 22, 2020

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bedevere-bot removed the awaiting merge label Sep 22, 2020

bedevere-bot added the awaiting changes label Sep 22, 2020

Reworded parts of the constants documentation

23ed559

Addresses python#22336 (comment), python#22336 (comment) & python#22336 (comment)

terryjreedy approved these changes Sep 22, 2020

View reviewed changes

bedevere-bot added awaiting merge and removed awaiting changes labels Sep 22, 2020

gvanrossum approved these changes Sep 22, 2020

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gvanrossum merged commit 0d0e9fe into python:master Sep 22, 2020

bedevere-bot removed the awaiting merge label Sep 22, 2020

BvB93 deleted the ellipsis branch September 28, 2020 16:51

xzy3 pushed a commit to xzy3/cpython that referenced this pull request Oct 18, 2020

bpo-41810: Reintroduce types.EllipsisType, .NoneType & `.NotImple…

be70ace

…mentedType` (pythonGH-22336) closes issue 41810

gvanrossum mentioned this pull request Nov 23, 2020

class ellipsis is public but shouldn't python/typeshed#3556

Closed

BvB93 mannequin mentioned this pull request Aug 30, 2023

Consider reintroducing types.EllipsisType for the sake of typing #85976

Closed

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bpo-41810: Reintroduce `types.EllipsisType`, `.NoneType` & `.NotImplementedType` #22336

bpo-41810: Reintroduce `types.EllipsisType`, `.NoneType` & `.NotImplementedType` #22336

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BvB93 commented Sep 22, 2020

	The sole value of the type :data:`types.NoneType`. ``None`` is frequently used to
	''None'' is the only instance of :data:`types.NoneType`. It is frequently used to

		Sole value of the type :data:`types.NotImplementedType` and a
		special value which should be returned by the binary special methods

	The same as the ellipsis literal "``...``" and sole value of the type
	The same as the ellipsis literal "``...``" and the only instance of

bpo-41810: Reintroduce types.EllipsisType, .NoneType & .NotImplementedType #22336

bpo-41810: Reintroduce types.EllipsisType, .NoneType & .NotImplementedType #22336

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bpo-41810: Reintroduce `types.EllipsisType`, `.NoneType` & `.NotImplementedType` #22336

bpo-41810: Reintroduce `types.EllipsisType`, `.NoneType` & `.NotImplementedType` #22336

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